[Alt-photo] The end of dichromate?

Don Bryant donsbryant at gmail.com
Mon Oct 5 14:01:43 UTC 2015


Thank you for your thoughtful reply.

I spent much of the day yesterday reading threads on APUG about DAS and
admiring the work, research, and application of DAS by Kees.

Actually I've been reading those posts since 2011, but I wanted to refresh
my memory of that activity.

Again thanks for the update and thanks for the link to your exhibit.

Don Bryant
On Oct 5, 2015 9:31 AM, "Jorj Bauer via Alt-photo-process-list" <
alt-photo-process-list at lists.altphotolist.org> wrote:

> Well, we might look at the CAS data for both.
>
> First up, Ammonium Dichromate, aka Chromic acid (H2Cr2O7) ammonium salt,
> CAS 7789-09-5:
>
>     http://img1.guidechem.com/msdspdf/7789-09-5.pdf
>
> Some highlights:
>
> Oxidizing solids (Category 2)
>   Carcinogenicity (Category 1B)
>   Germ cell mutagenicity (Category 1B)
>   Reproductive toxicity (Category 1B)
>   Acute toxicity, Inhalation (Category 2)
>   Acute toxicity, Oral (Category 3)
>   Specific target organ toxicity - repeated exposure (Category 1)
>   Acute toxicity, Dermal (Category 4)
>   Skin corrosion (Category 1B)
>   Respiratory sensitization (Category 1)
>   Skin sensitization (Category 1)
>   Acute aquatic toxicity (Category 1)
>   Chronic aquatic toxicity (Category 1)
>
> Risk of explosion by shock, friction, fire or other sources of ignition.
> Very toxic to aquatic organisms, may cause long-term adverse effects in
> the aquatic environment. May cause cancer. May impair fertility.
>
> The specific warnings for Ammonium Dichromate are numerous and dire. It's
> understandable why we have such a wealth of information on this substance,
> as it's been instrumental in so many industries and is also so dangerous;
> we needed this information to safely handle this stuff.
>
>
> Up next we have DAS, aka 4,4'-diazidostilbene-2,2'-disulfonic Acid
> Disodium Salt, CAS 2718-90-3:
>
>     http://img1.guidechem.com/msdspdf/2718-90-3.pdf
>
> Some highlights:
>
>     S22:Do not breathe dust .
>     S24/25:Avoid contact with skin and eyes .
>
>     May cause respiratory tract irritation.
>
>     May be harmful if absorbed through skin. May cause skin irritation.
>
>     Not a hazardous substance or mixture according to Regulation (EC) No.
> 1272/2008.
>     Not a hazardous substance or mixture according to EC-directives
> 67/548/EEC or 1999/45/EC.
> No component of this product present at levels greater than or equal to
> 0.1% is identified as probable, possible or confirmed human carcinogen by
> IARC.
>
> That's pretty much the entirety of the warnings for DAS. They're similar
> to the warnings for table salt (
> http://img1.guidechem.com/msdspdf/7647-14-5.pdf).
>
>
>
> While it may be that DAS doesn't have the wealth of scientific study
> behind it that dichromates do, it's believably less dangerous in all of the
> areas in which we do have data (not a carcinogen, not a mutagen, not highly
> flammable, not highly toxic).
>
> -- Jorj
>
>
>
> On 10/4/15 12:19 PM, Don Bryant via Alt-photo-process-list wrote:
>
>> I asked first Kees. Tell me why it's better. So far DAS seems like a pig
>> in
>> a poke.
>> On Oct 4, 2015 12:17 PM, "Kees Brandenburg via Alt-photo-process-list" <
>> alt-photo-process-list at lists.altphotolist.org> wrote:
>>
>> I'm skeptical about DAS being any less polluting than dichromates.
>>>>
>>> Hi Don, what knowledge makes you say that?
>>>
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